In a medium bowl, combine eggs, cucumber, walnuts, sweet pepper, chives, mayonnaise, sour cream, dill weed, mustard, salt and black pepper. Line bottoms of sandwich thins with spinach leaves. Divide egg salad evenly over spinach. Top with sandwich thin tops.
Tip: To hard cook eggs, place eggs in a single layer in a medium saucepan. Add enough cold water to cover the eggs by 1 inch. Bring to a rapid boil over high heat. Remove from heat, cover and let stand for 15 minutes; drain. Run cold water over the eggs until cool enough to handle. To peel eggs, gently tap each egg on the countertop. Roll the egg between the palms of your hands. Peel off eggshell, starting at the large end.